The present invention relates to a gas getter system and more particularly a gas getter system for use with vacuum insulation panels.
Getter materials, that is, materials which absorb or adsorb gases and vapors, including water vapor, are well known and are used in a wide variety of enclosures to continuously absorb various gases and vapors, depending on the particular getter material employed, to either protect the components located within the enclosure or to maintain a certain characteristic of the atmosphere within the enclosure, such as a dry atmosphere or a very low pressure atmosphere. One particular environment in which getter materials are used are vacuum insulation panels.
Vacuum insulation panels are known for various uses including use in refrigeration appliances where they greatly enhance the degree of thermal insulation within the cabinet of the appliance. Such panels must remain effective for the life of the appliance, generally a period in excess of 20 years. To do so, the panels must be highly gas impervious, yet must be able to prevent transmission of heat not solely by conduction and radiation through the panels, but also by conduction around the surfaces of the panels. Further, any gases and vapors that do permeate the panel walls in excess of what is tolerable, depending on the panel filler insulation material, must be absorbed or otherwise captured to prevent degradation of the panels which, for insulation purposes, are most effective only when the interiors of the respective panels are evacuated to a very low pressure by removal of nearly all gases and vapors (the desired vacuum level depends on the specific filler insulation material).
U.S. Pat. No. 5,018,328 entitled "MULTI-COMPARTMENT VACUUM INSULATION PANELS", assigned to the assignee of the present application, and incorporated herein by reference, discloses the use of a multi-compartment vacuum insulation panel. This panel utilizes multiple compartments to enhance the long term thermal characteristics of the panel by "protecting" the vacuum characteristics of at least one of the compartments by surrounding with additional evacuated compartments. Further, strategic placing of gettering materials is disclosed such that gettering material absorbing certain gases can be placed in the outer compartments and other gettering materials absorbing different gases can be placed in the internal compartments to enhance the lifetime of the panel.
U.S. Pat. No. 5,091,233 entitled "GETTER STRUCTURE FOR VACUUM INSULATION PANELS" also assigned to the assignee of the present application and incorporated herein by reference, discloses a handleable getter structure which permits the getter to be handled in open atmosphere for relatively short periods of time, yet provides prolonged gettering action over relatively long periods of time when used in a sealed compartment.
U.S. Pat. Nos. 4,000,246 and 4,938,667 disclose methods for evacuating compartments through the use of gettering material provided within the compartment. U.S. Pat. No. 4,938,667 also discloses the use of glass vials to hold the gettering material to prevent it from being exposed prematurely. Crushing of the glass vials will expose the gettering material at an appropriate time. However, such an arrangement is not useful within a vacuum insulation panel which typically has relatively thin plastic or foil walls which are susceptible to rupturing upon contact with broken glass.
U.S. Pat. No. 4,668,551 discloses a vacuum insulation panel having a single evacuated compartment filled with an insulating material and including two separately packaged getters to be contained within the evacuated compartment, one for absorbing carbon dioxide and the other for adsorbing freon gas.
U.S. Pat. No. 4,444,821 discloses a vacuum insulation panel which is filled with an insulating material and which also is provided with a combination of getter materials such as barium and zeolite for removing various gases from within the vacuum panel. It is disclosed that if both types of getters are employed as gettering materials within the vacuum insulating panel, it is preferred that they be disposed in different locations therein.
Thus, in known gettering systems, getters must be isolated from each other by being placed in separate compartments or else physically separated apart in a single compartment. However, even the physical separation will not prevent one of the getters from being consumed by gases or vapors to be absorbed by the second getter. These types of arrangements add to the time and cost involved in manufacture of vacuum insulating panels.